/*

 * Licensed to the Apache Software Foundation (ASF) under one

 * or more contributor license agreements.  See the NOTICE file

 * distributed with this work for additional information

 * regarding copyright ownership.  The ASF licenses this file

 * to you under the Apache License, Version 2.0 (the

 * "License"); you may not use this file except in compliance

 * with the License.  You may obtain a copy of the License at

 *

 *     http://www.apache.org/licenses/LICENSE-2.0

 *

 * Unless required by applicable law or agreed to in writing, software

 * distributed under the License is distributed on an "AS IS" BASIS,

 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.

 * See the License for the specific language governing permissions and

 * limitations under the License.

 */

package com.bff.gaia.unified.runners.fnexecution.translation;



import com.google.auto.value.AutoValue;

import com.bff.gaia.unified.model.pipeline.v1.RunnerApi;

import com.bff.gaia.unified.model.pipeline.v1.RunnerApi.ExecutableStagePayload.SideInputId;

import com.bff.gaia.unified.runners.core.construction.PTransformTranslation;

import com.bff.gaia.unified.runners.core.construction.graph.ExecutableStage;

import com.bff.gaia.unified.runners.core.construction.graph.PipelineNode.PCollectionNode;

import com.bff.gaia.unified.runners.core.construction.graph.SideInputReference;

import com.bff.gaia.unified.runners.fnexecution.state.StateRequestHandler;

import com.bff.gaia.unified.runners.fnexecution.state.StateRequestHandlers.SideInputHandler;

import com.bff.gaia.unified.runners.fnexecution.state.StateRequestHandlers.SideInputHandlerFactory;

import com.bff.gaia.unified.sdk.coders.Coder;

import com.bff.gaia.unified.sdk.coders.KvCoder;

import com.bff.gaia.unified.sdk.transforms.windowing.BoundedWindow;

import com.bff.gaia.unified.sdk.util.WindowedValue;

import com.bff.gaia.unified.sdk.values.KV;

import com.bff.gaia.unified.vendor.guava.com.google.common.collect.ImmutableMap;

import com.bff.gaia.unified.vendor.guava.com.google.common.collect.ImmutableMultimap;

import com.bff.gaia.unified.vendor.guava.com.google.common.collect.Multimap;



import javax.annotation.Nullable;

import java.io.ByteArrayInputStream;

import java.io.IOException;

import java.util.List;

import java.util.Map;



import static com.bff.gaia.unified.vendor.guava.com.google.common.base.Preconditions.checkArgument;



/** {@link StateRequestHandler} that uses a {@link SideInputGetter} to access side inputs. */

public class BatchSideInputHandlerFactory implements SideInputHandlerFactory {



  // Map from side input id to global PCollection id.

  private final Map<SideInputId, PCollectionNode> sideInputToCollection;

  private final SideInputGetter sideInputGetter;



  /** Returns the value for the side input with the given PCollection id from the runner. */

  public interface SideInputGetter {

    <T> List<T> getSideInput(String pCollectionId);

  }



  /**

   * Creates a new state handler for the given stage. Note that this requires a traversal of the

   * stage itself, so this should only be called once per stage rather than once per bundle.

   */

  public static BatchSideInputHandlerFactory forStage(

      ExecutableStage stage, SideInputGetter sideInputGetter) {

    ImmutableMap.Builder<SideInputId, PCollectionNode> sideInputBuilder = ImmutableMap.builder();

    for (SideInputReference sideInput : stage.getSideInputs()) {

      sideInputBuilder.put(

          SideInputId.newBuilder()

              .setTransformId(sideInput.transform().getId())

              .setLocalName(sideInput.localName())

              .build(),

          sideInput.collection());

    }

    return new BatchSideInputHandlerFactory(sideInputBuilder.build(), sideInputGetter);

  }



  private BatchSideInputHandlerFactory(

      Map<SideInputId, PCollectionNode> sideInputToCollection, SideInputGetter sideInputGetter) {

    this.sideInputToCollection = sideInputToCollection;

    this.sideInputGetter = sideInputGetter;

  }



  @Override

  public <T, V, W extends BoundedWindow> SideInputHandler<V, W> forSideInput(

      String transformId,

      String sideInputId,

      RunnerApi.FunctionSpec accessPattern,

      Coder<T> elementCoder,

      Coder<W> windowCoder) {



    PCollectionNode collectionNode =

        sideInputToCollection.get(

            SideInputId.newBuilder().setTransformId(transformId).setLocalName(sideInputId).build());

    checkArgument(collectionNode != null, "No side input for %s/%s", transformId, sideInputId);



    if (PTransformTranslation.ITERABLE_SIDE_INPUT.equals(accessPattern.getUrn())) {

      @SuppressWarnings("unchecked") // T == V

      Coder<V> outputCoder = (Coder<V>) elementCoder;

      return forIterableSideInput(

          sideInputGetter.getSideInput(collectionNode.getId()), outputCoder, windowCoder);

    } else if (PTransformTranslation.MULTIMAP_SIDE_INPUT.equals(accessPattern.getUrn())) {

      @SuppressWarnings("unchecked") // T == KV<?, V>

      KvCoder<?, V> kvCoder = (KvCoder<?, V>) elementCoder;

      return forMultimapSideInput(

          sideInputGetter.getSideInput(collectionNode.getId()),

          kvCoder.getKeyCoder(),

          kvCoder.getValueCoder(),

          windowCoder);

    } else {

      throw new IllegalArgumentException(

          String.format("Unknown side input access pattern: %s", accessPattern));

    }

  }



  private <T, W extends BoundedWindow> SideInputHandler<T, W> forIterableSideInput(

      List<WindowedValue<T>> broadcastVariable, Coder<T> elementCoder, Coder<W> windowCoder) {

    ImmutableMultimap.Builder<Object, T> windowToValuesBuilder = ImmutableMultimap.builder();

    for (WindowedValue<T> windowedValue : broadcastVariable) {

      for (BoundedWindow boundedWindow : windowedValue.getWindows()) {

        @SuppressWarnings("unchecked")

        W window = (W) boundedWindow;

        windowToValuesBuilder.put(windowCoder.structuralValue(window), windowedValue.getValue());

      }

    }

    ImmutableMultimap<Object, T> windowToValues = windowToValuesBuilder.build();



    return new SideInputHandler<T, W>() {

      @Override

      public Iterable<T> get(byte[] key, W window) {

        return windowToValues.get(windowCoder.structuralValue(window));

      }



      @Override

      public Coder<T> resultCoder() {

        return elementCoder;

      }

    };

  }



  private <K, V, W extends BoundedWindow> SideInputHandler<V, W> forMultimapSideInput(

      List<WindowedValue<KV<K, V>>> broadcastVariable,

      Coder<K> keyCoder,

      Coder<V> valueCoder,

      Coder<W> windowCoder) {

    ImmutableMultimap.Builder<SideInputKey, V> multimap = ImmutableMultimap.builder();

    for (WindowedValue<KV<K, V>> windowedValue : broadcastVariable) {

      K key = windowedValue.getValue().getKey();

      V value = windowedValue.getValue().getValue();



      for (BoundedWindow boundedWindow : windowedValue.getWindows()) {

        @SuppressWarnings("unchecked")

        W window = (W) boundedWindow;

        multimap.put(

            SideInputKey.of(keyCoder.structuralValue(key), windowCoder.structuralValue(window)),

            value);

      }

    }



    return new MultimapSideInputHandler<>(multimap.build(), keyCoder, valueCoder, windowCoder);

  }



  private static class MultimapSideInputHandler<K, V, W extends BoundedWindow>

      implements SideInputHandler<V, W> {



    private final Multimap<SideInputKey, V> collection;

    private final Coder<K> keyCoder;

    private final Coder<V> valueCoder;

    private final Coder<W> windowCoder;



    private MultimapSideInputHandler(

        Multimap<SideInputKey, V> collection,

        Coder<K> keyCoder,

        Coder<V> valueCoder,

        Coder<W> windowCoder) {

      this.collection = collection;

      this.keyCoder = keyCoder;

      this.valueCoder = valueCoder;

      this.windowCoder = windowCoder;

    }



    @Override

    public Iterable<V> get(byte[] keyBytes, W window) {

      K key;

      try {

        // TODO: We could skip decoding and just compare encoded values for deterministic keyCoders.

        key = keyCoder.decode(new ByteArrayInputStream(keyBytes));

      } catch (IOException e) {

        throw new RuntimeException(e);

      }

      return collection.get(

          SideInputKey.of(keyCoder.structuralValue(key), windowCoder.structuralValue(window)));

    }



    @Override

    public Coder<V> resultCoder() {

      return valueCoder;

    }

  }



  @AutoValue

  abstract static class SideInputKey {

    static SideInputKey of(Object key, Object window) {

      return new AutoValue_BatchSideInputHandlerFactory_SideInputKey(key, window);

    }



    @Nullable

    abstract Object key();



    abstract Object window();

  }

}